Owen Barfield regarded Rudolf Steiner as his master, as indeed one of the great thinkers of human history (of a stature comparable to Aristotle); and devoted much of his life to working for the Steiner's cause.
Nonetheless, in terms of Steiner's own writings for the public, Barfield's direct advocacy of Steiner was selective:
1. Christian Framework
Barfield shared Steiner's Christian Framework - although he wrote about it less often than did Steiner. Barfield regarded the birth, life, death and resurrection of Christ as the central and dividing event in cosmic history.
(Barfield, also shared Steiner's unorthodox - but Gospel-based - explanation of the dual God-Man nature of Jesus Christ as having been some kind of combination of two persons.)
2. Steiner's Philosophy.
My impression is that Barfield especially valued Steiner's philosophical works: that is his three early books - the first one sometimes translated as the Theory of Knowledge Implicit in Goethe's World Conception (1886) was one that Barfield sometimes described as Steiner's least read but most important book; the other two are Steiner's PhD thesis Truth and Knowledge (1892) and the Philosophy of Freedom/ Spiritual Activity (1896).
Steiner's ideas are usually described as setting-out an Epistemology (that is, a theory of knowing and valid knowledge) but I personally regard them as being more fundamental than that, and instead describing a metaphysics (that is setting-out the fundamental nature of reality).
For example; Steiner regarded the activity of Thinking as a the primary reality, and attempted to argue and prove this 'epistemologically' by evidence and reason and without discussion first assumptions. However, I would suggest that this is actually a metaphysical assumption, not an obvious conclusion - especially since this view about the primacy of Thinking seems to have been unique to Steiner at the time it was made.
(I should point-out that I personally accept this assumption of the primacy of thinking - which I regard as a major and essential breakthrough in human self-understanding; but I accept it on intuitive grounds, and not because of the 'evidence' for it.)
3. What Barfield does not mention (much)
Beyond Steiner's basic philosophy; Barfield accepted and advocated Steiner's vision of world history as an evolution of consciousness - through different stages, starting with an un-free, disembodied state of total consciousness with no discrete 'self'; and incrementally moving through incarnation towards modern Man's state of alienated freedom, without consciousness of anything outside The Self.
Barfield's future destination of Final Participation corresponds to Steiner's Spiritual Soul - as being a state which combines freedom and consciousness for the first time. However, Steiner mapped-out a timetable for the evolution of consciousness, projected hundreds, even thousands, of years into the future; and Barfield did not seem to endorse this in his writings.
Nor did Barfield say much about the vast body of highly detailed and specific Spiritual Science (in agriculture, education, medicine, politics etc. etc.) which Steiner gave in the lectures of his last couple of decades. My impression is that Barfield was broadly in agreement with Steiner on these matters (eg in education Barfield supported Waldorf schools, and in politics the 'threefold' analysis ad recommendations); but Barfield could not confirm all of the many specifics of Steiner's output from his personal knowledge, and so said little about is.
The reason for this differential emphasis is probably that Barfield distinguished between those aspects of Steiner which he had personally validated and those aspects which he had not. Indeed, since Steiner was astonishingly productive of ideas and assertions (having given some hundreds of transcribed lectures per annum in his later years); so it would probably not be possible (even in principle, and even in so long as life as Barfield enjoyed) to check and validate everything that Steiner said.
On top of this; Steiner said at times (although he rather contradicted by his practice) that his intuitive and meditational methods of deriving Spiritual Science data were prone to error, and that therefore not everything he stated was expected to be correct; but that all should be testable by all properly-motivated people who were able to practice the Anthroposophical method, and who made the effort.
(Not many seem to have done this - Valentin Tomberg was an example of someone who, after Steiner's death, extended and re-worked Steiner's statements in a Platonic direction; and he was made to resign from the Anthroposophical Society as a result!)
In sum, I think that Barfield wholly endorsed Steiner's philosophy and his method ie. his Anthroposophy; however, while not explicitly rejecting it, he was somewhat partial in his endorsement of the many details of Steiner's findings ie. his Spiritual Science.
I would indeed put it more strongly: Steiner's basic analysis and the method of Anthroposophy is of vital importance to everybody; but the many thousands of stated findings of specific assertions of Spiritual Science are not essential, and indeed are mostly wrong.
In a nutshell: Barfield contains the necessary essence of Steiner. Most people will therefore want to approach Steiner via Barfield; turning to Steiner himself mainly for another perspective, and a different mode of explanation.
Note: I personally believe that the above is the best way for most people to approach the work of Rudolf Steiner; certainly it is what I do. Most of the vast body of purported fact that Steiner generated I ignore - furthermore I do not believe that human destiny unrolls according to a calendar projected millenia into the future.
For this reason, for most people, it is probably best to approach Steiner via Barfield; since Barfield includes the best of Steiner and leaves-out the parts that are generally regarded (or at least I regard!) as unacceptable.
Nonetheless, it is well worth reading the three early books of Steiner's at least - because these are potentially life-changing works of genius; and reading Steiner more widely but more selectively for the many insights scattered elsewhere. For example, my favourite thing of his is the 1918 lecture The work of the angel/ in Man's Astral Body. With Steiner - starting from the 1886 book on Goethe, by and large - the earlier the work, the better it is, and the later the more compromised.