http://revach.net/article.php?id=5282

Section: Halacha   Category: Tshuvos
Rav Moshe Feinstein - Counting Sefira & Eating Before a Late Maariv
The Mishna Brura (489:2) paskens that on the first night of Sefiras HaOmer one should count as soon as possible in order that the Sefira should be temimos, complete. The Chayei Adam (131) and many other poskim hold that this applies to every night of Sefira and one should try to daven Maariv as close to the Zman as possible.

According to this it would seem that if a person always davens by a late Minyan for Maariv he should count sefira by the Zman and daven Maariv later. However, the poskim agree with the Chok Yaakov that one should daven Maariv before counting sefira, since Maariv is Tadir and therefore the more common mitzva comes first.

What happens, asks Rav Moshe Feinstein (Igros Moshe OC 4:98), if a person wants to eat and does not want to wait until after Maariv, may he then count before Maariv? Rav Moshe says that he should not count before Maariv, yet he may eat. The reason is that although one may not eat before Shema, he may eat before Maariv if he davens at a Minyan Kavua. Therefore, says Rav Moshe, the heter to eat before Shema extends to Sefira as well, since Sefira is less strict than Shema.

Important Note: We bring this tshuvah as a starting point for discussion and not to convey any halacha. We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. One should learn the tshuva to verify the accuracy of our interpretation. Please understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.