Oscar is a true barnyard mix so this is just for fun! I really enjoy learning about breed features/traits that people point out. So if you would so graciously oblige......
Possible hens: Rhode Island Red, Buff Orpington, Wyandotte, Light Brahma, Plymouth Rock, Welsummer, Brown Leghorn, Speckled Sussex, Easter Egger
Oscar's mother is not a Light Brahma.
--Light Brahmas usually pass feathered feet to their offspring.
--Light Brahmas usually pass pea comb to their offspring.
--Oscar has a golden color. Gold is recessive to silver, so him looking gold means he inherited the gold gene from both parents. But Light Brahmas are silver, not gold, so a Light Brahma cannot be Oscar's mother.
Oscar's mother is probably not a Wyandotte.
Wyandottes are supposed to have rose combs, and should pass those rose combs to their chicks. But Oscar does not have a rose comb.
Wyandotte parents do sometimes produce chicks with single combs, which is why I said "probably" not a Wyandotte mother, instead of being entirely sure.
Oscar's mother is probably not an Easter Egger, because so many Easter Eggers have pea combs, and pass those to their chicks. Oscar does not have a pea comb. (But there are some Easter Eggers with not-pea combs, so I cannot completely rule out the Easter Eggers.)
It looks like Oscar has white legs. Do you know what color legs his father had?
Orpingtons and Sussex should have white legs, Easter Eggers often have green legs, and the other breeds on your list should have yellow legs.