The "oa" in the word "broad" is pronounced like the words "or" or "awe". In phonetic symbols that is ɔː . However in all other examples I can think of it is pronounced like the "oe" in "toe". Or in phonetic symbols, əʊ . For example, in goat, toast, oat and so on.
Etymology: Common Germanic: Old English brád , identical with Old Frisian brêd , Old Saxon brêd (Middle Dutch breet -d- , Dutch breed ), Old High German (Middle High German and modern German) breit , Old Norse breið-r , (Swedish, Danish bred ), Gothic braiþ-s < Old Germanic *braido-z : no related words are known even in Germanic, except its own derivatives
Although perhaps not directly relevant to the question, where it makes a difference I am talking about British English pronunciation. So broad is pronounced /brɔːd/ , both or and awe are pronounced /ɔː/, toe is pronounced /təʊ/, goat is pronounced /ɡəʊt/ and so on and so forth.