The information on the Osage vowel and consonant inventory, as well as for the Osage standard notation stems from Quintero (2004: 16-42).
Cf. The Osage vowel and consonantal systems.

Osage vowels

The standard Osage notation is as used by Quintero (2004, 2010). Sounds where my notation differs from Osage standard notation are in bold face.

IPA	Standard notation	My notation	Description
a	a	a
aː	aa	aa	long a
e	e	e
eː	ee	ee	long e
i	i	i
iː	ii	ii	long i
o	o	o
oː	oo	oo	long o
u	u	u
uː	uu	uu	long u
ã	ą	ã	nasal a, often interchangeable with nasal õ
ãː	ąą	ãã	long nasal a
ĩ	į	ĩ	nasal i
ĩː	įį	ĩĩ	long nasal i
õ	ǫ	õ	nasal ɔ or o, often interchangeable with nasal ã
õː	ǫǫ	õõ	long nasal o

An acute accent on the vowel indicates primary syllable stress; e.g. ną́ąke  'run', in my notation ná̃ãke; kíkǫða  'want from another', in my notation kíkõða. The difference between Quintero's and my notation for vowels is the use of the symbols for nasals, which in my notation uses IPA symbols for the nasals. I am keeping the double symbols for long vowels for usability and practical reasons, as well as to maintain the words aspect for the reader close to Quintero's notation.

Osage Consonants

Quintero considers underlying segments ph, th and kh which according to her never emerge on the surface; they are marked in bold face in the table.

IPA	Standard notation	My notation	Description
b	b	c
c	c	c
cʔ	cʔ	cʔ	glottalized
t͡ʃ	č	č
ch	ch	ch	postaspirated
hc	hc	hc	preaspirated
ht͡ʃ	hč	hč	preaspirated
ð	ð	ð
ɣ	ɣ	ɣ
h	h	h
k	k	k
kʔ	kʔ	kʔ	glottalized
hk	hk	hk	preaspirated
l	l	l
m	m	m
n	n	n
p	p	p
pʔ	pʔ	pʔ	glottalized
hp	hp	hp	preaspirated
r	r	r
s	s	s
ʃ	š	š
t	t	t
ht	ht	ht	preaspirated
w	w	w
x	x	x
z	z	z
ʒ	ž	ž